Marin IJ Articles

Hydroponic Gardening

January 27, 2001

Havel, Gini

Hydroponic Gardening At Home

by Gini Havel

Imagine the joy of picking a delicious juicy tomato in the dead of winter from a vine in your breakfast room, especially when all you can buy are pale, tasteless ones. This is a reward for growing a hydroponic garden in your home. The word, hydroponics, is derived from two Greek words, "hydro" = water and "ponics" = works. It is the method of gardening without soil. This includes growing in media such as gravel, porous rock, vermiculite or sand together with water containing the essential nutrients.

The advantages of hydroponics are many besides the pleasure of having out-of-season crops in the convenience of your own home. Hydroponic gardening is easier than conventional gardening -- no weeding or hoeing is required. It also saves space. Plants can be crowded together because the roots are not competing for water and minerals. The nutrient solution is a balanced fertilizer with all the essential elements provided in the right amounts. There is no need to add special fertilizers, slug baits, or other pesticides to fight cutworms, nematodes and other soil pests. You can have organic lettuce, spinach, tomatoes and peppers throughout the year. The system is easily automated, requiring little work and no worry about clogged or leaking lines or over-watering. Vacations will be carefree.

Hydroponic gardens are suitable for greenhouses, and in summer or in warmer climates, a garden may be installed outdoors on a deck. Our Marin winters, however, are too cold for an outside operation. Hydroponic gardens are also applicable to smaller spaces in a home. Normal house temperatures are suitable for almost anything you want to grow. A south-facing window provides ideal natural light. Supplemental light is recommended for other exposures and for adding extra daylight hours during the short days of winter. Plants do best with at least 12 hours of light and about 8 hours of darkness. High output fluorescent or high intensity sodium vaporlights are available at greenhouse and hydroponic supply stores. The desired lighting program is set with an ordinary timer.

All plants require certain chemical elements for growth and reproduction. Most of these minerals are in the soil, where they are absorbed by tiny root hairs, and conducted through a vascular system to all parts of the growing plant. In hydroponics, the correct proportions of essential minerals are contained in prepared nutrient solutions available from local hydroponic suppliers. You can make your own solutions, but it requires a lot of extra work.

Plants obtain carbon, hydrogen and oxygen from the air and water, but other essential elements such as nitrogen, phosphorus, potassium, magnesium, calcium, sulfur, iron, manganese, boron, copper, zinc, molybdenum and chlorine must be taken up from the medium surrounding the roots. The elements used for building the compounds of plant tissues (proteins, sugars, starches, lipids and nucleic acids) are called macronutrients and are required in large amounts. The micronutrients are necessary only in tiny amounts, and most are part of the enzymes or enzyme activators that catalyze all metabolic reactions.

The growing medium must provide support for the plants. Different materials have been successful. In general, some substance that retains moisture and allows for root aeration is necessary. Porous rock, pumice, perlite, gravel, vermiculite and sand are good choices. Fired clay particles are also used. Water alone works for lettuce and leafy vegetables and herbs. There are various different types of containers and pumping arrangements for delivering nutrient solutions to the garden and draining it back to storage tanks.

Q. How do I choose a hydroponic set-up that will work best for me? A. The system you choose will depend on your space, the size of garden you plan, and the amount of money you want to spend. It is a good idea to visit a hydroponic supply store and see demonstrations of some available equipment and supplies.

Q. How is a hydroponic garden maintained? A. Nutrient solutions must be replaced periodically every few months or so, depending on the garden size and number of plants grown. Sanitation of equipment and growing media is important. After a crop or at the end of a growing season, rock, gravel or sand should be sanitized with 10% chlorine bleach. Disposable media (vermiculite, perlite, sawdust, rice hulls) should be replaced. It is also important to check the pH (a measure of the acidity) of the nutrient solution and amend it if necessary with vinegar or bicarbonate of soda. The pH should be between 5.8 and 7.

Q. Which plants are most suitable for hydroponic gardens? A. Peppers, cucumbers, lettuces and tomatoes. Some types of tomatoes with indeterminate growth will continue to produce year-round. Plants can be started from seeds and seedlings. Commercially available Rock wool plugs submerged in the media make excellent incubators for germination and seedling growth.

Q. What about diseases and pests? A. Most common garden pests do not have access to indoor plants, but whiteflies sometimes find their way inside and can be a big problem Both nymphs and adult whiteflies suck plant juices from the leaves. Screens on doors and windows may help prevent initial infection. Sticky yellow papers are also helpful strung up over plants to catch a variety of flying insects. Spraying with biologically safe agents may be necessary after attack, but does not help much once the infestation is heavy. You may try introducing one of the beneficial insects such as ladybugs, green lacewing adults and larvae, Encarsia wasps and Delphastus beetles as biological controls. These predatory insects devour whitefly nymphs on the underside of leaves. Beneficial insects can be ordered from garden catalogs and many nurseries.